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Find a percentage of a number, or add or subtract a percentage. See the formula and a worked example.
Calculate the percentage increase or decrease between an original value and a new value, with the absolute difference.
Calculate a discounted price and how much you save. Enter any price and a discount from 0% to 100%.
Find the arithmetic mean, sum and count of a list of numbers. Enter values separated by spaces or semicolons.
Solve a direct proportion a : b = c : x. Enter three values to find the missing fourth value.
Reduce a fraction to its simplest form and see its decimal value. Enter an integer numerator and a positive denominator.
Count calendar days and weeks between two dates, excluding the starting day. Leap years are included automatically.
Calculate completed years and total days between a birth date and a reference date, including leap years.
Convert metres, kilometres, centimetres, inches, feet, yards and miles using fixed conversion factors.
Convert kilograms, grams, milligrams, tonnes, pounds and ounces. See the factors behind each mass conversion.
Convert square metres, square centimetres, square kilometres, hectares, square feet and acres.
Convert litres, millilitres, cubic metres, US liquid gallons and US fluid ounces with explicit unit definitions.
Convert kilometres per hour, metres per second, miles per hour and knots. Compare speeds in familiar units.
Convert seconds, minutes, hours, fixed 24-hour days and seven-day weeks. Decimal time values are supported.
Convert watts, kilowatts, megawatts and mechanical horsepower. Power units are separate from energy units.
Convert Celsius, Fahrenheit and Kelvin. The calculator checks absolute zero and shows the temperature conversion formula.
Find the share of a positive total. The part and total must use the same measurement or currency.
Recover a value before a percentage increase. Enter a negative rate to reverse a reduction smaller than 100%.
Compare two rates in percentage points. Moving from 20% to 25% is 5 points, not a 5% relative increase.
Reduce two positive whole quantities to an equivalent integer ratio using their greatest common divisor.
Estimate time when equally productive workers share a fixed task. Doubling workers halves time under this ideal assumption.
Find the greatest positive integer dividing both inputs. The second integer must be positive; the first may be zero.
Find the smallest positive multiple shared by two positive integers. Useful for synchronizing repeating intervals.
Multiply consecutive positive integers up to n. Large outputs are floating-point approximations; 0! is defined as 1.
Count selections without replacement when order does not matter. The selected count cannot exceed available items.
Count ordered selections without replacement. Selecting A then B differs from selecting B then A.
Raise a base to a real exponent. Negative bases require exponents yielding real values; undefined or infinite results are rejected.
Find the nonnegative number whose square equals the input. Negative inputs have no real square root.
Find the real cube root of a positive or negative number. For example, the cube root of −8 is −2.
Find a real root of integer degree. A negative radicand requires an odd degree; the principal nonnegative root is used otherwise.
Calculate a logarithm in any positive base except one. Both the number and base must be positive.
Express a number as a mantissa and a power of ten. Zero is displayed separately because it has no unique normalized exponent.
Round to up to eight decimal places using JavaScript Math.round, which resolves exact halfway values toward positive infinity.
Divide nonnegative integers and show the integer quotient and remainder. The divisor must be positive.
Solve a quadratic equation with real coefficients and real roots. The leading coefficient must be nonzero and the discriminant nonnegative.
Solve a single linear equation. A zero coefficient does not determine one unique solution and is rejected.
Find the nth term and sum of an arithmetic sequence, where each term changes by the same fixed amount.
Find the nth term and finite sum when every term is multiplied by a constant ratio. Ratio one uses n times the first term.
Find the slope between two points. Vertical lines have undefined slope and cannot be represented by this numeric result.
Find the point halfway along a straight segment in a two-dimensional Cartesian coordinate system.
Calculate straight-line Euclidean distance in a plane. Coordinates must use the same scale; this is not road or geographic distance.
Find the hypotenuse of a right triangle from its perpendicular legs. Both legs must use the same length unit.
Convert angular degrees to radians without wrapping the angle. A full turn is 360 degrees or 2π radians.
Calculate sine, cosine and tangent of an angle in degrees. Tangent is undefined at odd multiples of 90 degrees.
Convert a nonnegative safe integer into its binary representation. Fractional values and integers above JavaScript safe precision are excluded.
Convert a nonnegative integer to hexadecimal digits 0–9 and A–F. This does not interpret signed machine-word formats.
Find area, perimeter and diagonal of a square. Enter the side in one consistent unit; area uses its square.
Find the area, perimeter and diagonal of a rectangle using perpendicular length and width in the same unit.
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Maths
Choose the operation that matches your percentage, ratio or equation problem. Match each symbol in the formula to the example input.
Dates & age
Choose elapsed days, calendar position or completed age according to your question. Date conventions matter at month ends and around leap days.
Unit converters
Select the quantity, then choose its source and destination units. Read variant names before converting units with similar labels.
Geometry
Choose a shape and enter the dimensions its formula requires. Check whether each label asks for a radius, diameter, perpendicular height or semiaxis.
Statistics
Choose the measure that matches your question about centre, spread or probability. Sample estimates, population measures and probability models use different assumptions.
Everyday money
Separate price, tax, fees and repayments with the calculator that matches your transaction. Compare scenarios using the same currency and cost basis.
Physics
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Home & construction
Estimate material quantities or project costs from measured dimensions. Choose the tool matching the material and measurement before comparing prices.
Investing
Choose a one-time investment, regular contributions or deposit model that matches your cash flows. Compare total contributions alongside projected value.